A henge is a roughly circular or oval-shaped flat area enclosed and
delimited by a boundary earthwork - usually a ditch with an external
bank.

The most distinctive components of any henge monuments
are its bank and ditch. Most henges have either a single ditch or
a pair of concentric ditches surrounding the central area.

This
is not always the case, however, with some henges having no ditch
while others have three.

The soil and bedrock taken from the ditch was
used to build the henge bank which generally lay outside the ditch.
The sizes of the banks varied proportionally with the size of the
ditches. Typically, however, they seem to have been fairly broad
at the base, five metres to 30 metres wide and up to five metres
high.

Access to the central area was via formal entrances
through the earthwork. Most henges have either one entrance or two
opposed entrances.

The alignment of henges seen in the position of
their entrances is highly variable and may have been as much conditioned
by local geography as by any preferred orientation. There is, however,
a slight tendency for henges with a single entrance to have that
entrance set in the north or north-east sector while sites with
two entrances are aligned SE-SSE to NW-NNW or ENE-E to WSW-W.

The original purpose and function of henge monuments
is not fully understood. Because of the arrangement of banks and
ditches it is generally accepted that they are ceremonial or ritual
monuments.

Henges are generally classified into four main
types according to the number of entrances and ditches they have.
The traditional classification is as follows:

Class I

Single entrance, single
bank, and, usually, a single ditch circuit.

Class IA

Single entrance, single
bank, and double circuit of ditches.

Class II

Two opposed entrances,
single bank, and single ditch circuit.

Class IIA

Two opposed entrances,
single bank, and two or more circuits of ditches.